Alarm apparatus



Nov. 11, 1969 H. EISENBERG ALARM APPARATUS Filed March 10, 1967 I N VEN TOR HAROLD EISENBERG ATTQRNEY United States Patent 3,478,352 ALARM APPARATUS Harold Eisenberg, Chicago, Ill., assignor to Honeywell Inc., Minneapolis, Minn., a corporation of Delaware Filed Mar. 10, 1967, Ser. No. 622,118 Int. Cl. G08b 29/00 U.S. Cl. 340-409 6 Claims ABSTRACT OF THE DISCLOSURE A security monitor alarm apparatus to provide an alarm indication when the current in a supervised line either increases or decreases by a set amount. The security monitor supervises the remote lines to alarm switching means which may be installed across the line to provide an increase in current when the device is operated or in series with the line to provide a decrease in current when the device is operated. An alarm condition is indicated both visually and audi-bly. A normally operating oscillatory circuit in the apparatus aids in selfchecking the apparatus for operability.

BACKGROUND OF THE INVENTION The field of art to which this invention pertains is the alarm art and more particularly condition responsive electrical alarm apparatus. Solid state signalling circuits of the type used in providing central station electrical protection of property from the hazards of intruders, fire or other abnormal conditions are known in the art. In the past, however, this solid state circuitry has been of a passive nature under normal conditions so that if failure of the solid state components occurred there would be no indication of that failure. In applicants invention the solid state circuitry is active during normal operating conditions so that any failure in the solid state circuitry will result in a communication of that fact to the apparatus operator.

SUMMARY OF THE INVENTION A solid state alarm apparatus for sensing and indicating an increase or a decrease in supervisory current. The apparatus includes a normally operative oscillator circuit feeding a pulsing type signal through a solid state circuit to indicate normal conditions, the oscillatory circuit being so biased as to be disabled by a change in the supervisory current.

BRIEF DESCRIPTION OF DRAWING The single figure of the drawing is a schematic representation of the circuit of a preferred embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawing, there is disclosed a security line monitor apparatus adapted to be energized from a suitable source of DC potential at terminals 10 and 11. The positive terminal 10 is connected by a conductor 12 through a conventional voltage regulator 13 to provide a regulated DC potential on a conductor 14.

3,478,352 Patented Nov. 11, 1969 A monitor line voltage divider may be traced from the conductor 14 comprising a plurality of temperature compensated resistive elements including a resistor 15, a potentiometer 16, a junction 17, resistor 20, a junction 21, a potentiometer 22, a resistor 23, a shorting switch 24 paralleling resistor 23, to a junction 25 and the terminals of a Secure-Access double-pole double-throw reversing switch 26. The monitor line continues through the reversing switch, through a transmission line or remote line 31 by way of a terminal 30, to an end-of-line terminating resistor 32, back through the other side 31' of the remote line, through a terminal 33 and switch contacts 26 to ground.

The reversing switch 26 has a pair of movable contacts 34, 35 and 38, respectively, making contacts in one position with stationary contacts S, S and S and in the opposite position with stationary contacts A, A and A". Stationary contacts S and A are connected to ground while the contacts A and S' are directly connected together at the junction 25. The transmission line or remote line 31, 31' which is to be supervised, and which terminates in resistor 32 at the remote station, may also include sensing elements at the remote station such as a normally open responsive switch 36 connected in shunt with the remote line and a normally closed condition responsive switch 37 connected in series with the line 31. The elements 36 and 37 maybe fire responsive, intruder responsive, or the like and may represent entire systems of this nature at the remote station.

The junction 17 on the monitor line is connected through a resistor 40 to the base electrode of an NPN transistor Q1, the collector electrode of Q1 being directly connected to a junction 41 on the conductor 14 and the emitter electrode of Q1 being connected through a resistor 42 to ground. The emitter of Q1 is also connected by a conductor 43 to the base electrode of a PNP transistor Q2, the collector of which is grounded. The emitter of transistor Q2 is connected through a resistor 44, a junction 45, and a conductor 46 to the emitter electrode of a unijunction transistor Q5.

The junction 21 on the monitor line is connected by a resistor 50 to the base electrode of a PNP transistor. Q3, the collector electrode of which is grounded. The emitter electrode of Q3 is connected through a resistor 52 to a junction 51 on the conductor 14 and is also dir ectly connected by a conductor 53 to the base electrode of an NPN transistor Q4. Transistor Q4 has its collector directly connected to the junction 51 and its emitter electrode connected through a resistor 54, a temperature compensating thermistor S5 and a potentiometer 56 to the junction 45 and thus to the emitter of unijunction transistor Q5.

Base 1 of unijunction transistor Q5 is connected by means of a resistor 60, a junction 61 and a resistor 62 to a junction 63 on the regulated DC conductor 14. Base 2 of Q5 is connected through the primary winding 64 of a pulse transformer T1 to ground. A voltage divider also exists from junction '61 to ground comprising a resistor 65, a potentiometer 66 having a wiper 67, and a resistor 68. A capacitor 70 is also connected between junction 61 and ground. The wiper 67 of potentiometer 66 is connected through a pair of parallel back-to-back diodes 71 to the emitter of unijunction Q5, the wiper 67 further being connected through a timing capacitor 72 to ground. This circuit forms a relaxation oscillator trigger circuit.

The pulse transformer T1 which has its primary winding 64 connected in the output circuit of the oscillator Q also includes a secondary winding 73, the lower terminal of which is grounded and the upper terminal of which is connected through a diode 74, a junction 75 and a capacitor 76 to the base electrode of an NPN transistor Q6. A pulse stretching network comprising a capacitor 77 paralleled by a resistor 78 is connected between the junction 75 and ground. The transistor Q6 also includes a collector electrode which is connected by means of a resistor 80 to the positive conductor 12, and further includes an emitter which is connected through a resistor 81 paralleled by a capacitor 82 to ground. A bias resistor 83 connects the base electrode of Q6 to the positive conductor 12 to bias it normally to saturation.

The output signal from Q6 is taken from the collector through a coupling capacitor 84, a conductor 85 and the contacts 1K1 of a relay 1K to the base electrode of an NPN transistor Q7. A resistor 86 also connects the conductor 85 to ground. The transistor Q7 has an emitter electrode which is directly connected to the base electrode of another transistor Q8. The collector electrodes of both Q7 and Q8 are directly connected to the positive conductor 12. Q8 also includes an emitter electrode which is connected through the winding of relay 1K to ground, this winding being paralleled by a smoothing capacitor 90. Relay 1K includes in addition to the contact 1K1 a further double-throw contact 1K2 and a third contact 1K3. The contacts of relay 1K are shown in their de-energized position.

The relay contact 1K2 comprises a movable portion energized from conductor 12 and a pair of stationary portions 91 and 92. The stationary contact 91 is connected through an incandescent lamp 93 and a resistor 94 to ground. The stationary contact 92 is directly connected to the movable contact 38 of the Secure-Access switch 26, described above, which contact 38 makes with stationary contact S" or A". The stationary contact S is connected through a Secure incandescent lamp 95 and the resistor 94 to ground. Likewise, the contact A" is connected through an Access incandescent lamp 96 and the resistor 94 to ground. Thus one of the three indicator lamp bulbs is normally illuminated depending upon the position of the relay switch 1K2 and the Secure-Access switch 26.

A double-pole double-throw Reset switch is operatively connected into the above described circuitry and includes a first movable pole portion 100 which makes contact with stationary contacts 101 or 102 and a second movable pole portion 103 which makes contact with stationary contacts 104 or 105, respectively. The contact 101 is connected by a resistor 106 to the base of transistor Q7 while the movable pole 100 is connected by means of a capacitor 107 to the supply conductor 12 and the stationary contact 102 is connected by a resistor 108 to the supply conductor 12. The movable pole 103 is connected by a capacitor 110 to ground, the stationary contact 104 is connected by a resistor 111 to ground and the stationary contact 105 is directly connected to the junction 21 on the monitor line.

A further circuit may be traced from the conductor 12 through a resistor 112, a junction 113, the relay contacts 1K3, a junction 114, from anode to cathode of an SCR Q9 and through a resistor 116 to ground. A further voltage divider can be traced from junction 114 through a resistor 115, which is paralleled by a capacitor 117, a junction 120 and a resistor 121 to ground. The junction 120 is directly connected to the gate electrode of the SCR. The cathode of the SCR Q9 is also connected by means of a conductor 122 and a diode 123, an output terminal 124. This output terminal 124 is adapted to energize an audible alarm such as a hell, not shown. A

Silence single-pole double-throw switch has a movable contact 125 and a pair of stationary contacts 126 and 127. The stationary contact 126 is directly connected to the junction 113 and is also connected by a capacitor 130 to ground. The stationary contact 127 is connected by a resistor 131 to a junction 132 on the conductor 122. Also the movable contact 125 is connected through a capacitor 133 to the junction 132.

OPERATION In considering the operation of the apparatus it is to be generally understood that the security monitor will be used to provide an alarm indication when the current in the supervised line either increases or decreases by a set amount from the normal value. An alarm condition is indicated both visually and audibly and the alarm locks in until reset is provided. Generally, the normal conditions are that transistors Q1 and Q3 are conductive, transistors Q4 and Q2 are normally non-conductive, unijunction Q5 is oscillating, the oscillator pulses are being transmitted through Q6, Q7 and Q8 to maintain relay 1K energized so that the SCR Q9 is non-conductive, the bell is silent and either the Access or Secure lamp is illuminated.

Considering in greater detail the operation of the line monitor, the monitor line is essentially a series circuit comprising the resistive elements 15, 16, 20, 22, 23 and the external remote terminating element 32. Under normal conditions the potentials at the two monitoring points 17 and 21 remain substantially constant. Any tampering with the monitor line that will cause a deviation in the line current, 5% for example, will set the unit into an alarm condition. Thus, if the terminating resistor 32 is shorted, or the monitor line is open, the alarm current is changed setting the unit into an alarm condition. The potentiometer 16 is connected as a rheostat and is used to adjust the monitor line current to the desired value. The potentiometer 22, also connected as a rheostat, is adjusted so that the sum of its resistance and the resistance of the transmission line 31, 31' will together total a given resistance value. The resistor 23 together with shorting switch 24 is operative for field adjustment of the equipment.

Again assuming normal monitor line conditions, the potentials at junctions 17 and 21 are such that the transistors Q1 and Q3 are both maintained conductive. As a result, the transistors Q2 and Q4 are both biased nonconductive and thus do not load the relaxation oscillator unijunction transistor Q5. When transistors Q2 and Q4 are not conducting, the unijunction Q5 is allowed to repetitively pulse in an oscillating fashion. This occurs because the capacior 72 is allowed to charge from the voltage divider including resistor 65, potentiometer 66, and resistor 68. When the potential on capacitor 72 reaches the firing point of unijunction Q5, it conducts to discharge capacitor 72 and provide a pulse through transformer T1. This action is repetitive and continuous so that a train of pulses is generated.

Secondary winding 73 of the pulse transformer and the rectifier 74 are poled to allow negative pulses to appear at junction 75. The capacitor 77 and resistor 78 function as a pulse stretcher. The continuing stream of negative stretched pulses is coupled through capacitor 76 to the base of the normally saturated transistor Q6. Each of these pulses temporarily brings the transistor out of saturation towards cutotf resulting in a similar stream of positive pulses at the collector of Q6. As long as these pulses continue to appear at the base of Q7, the transistors Q7 and Q8 conduct and relay 1K is maintained energized whereby contact 1K1 is maintained closed, contact 1K3 is maintained open and contact 1K2 makes contact with fixed terminal 92.

In order to establish this condition initially, the reset switch, preferably a push-button switch, is actuated. This connects both terminals of capacitor 107 to the conductor 12 to discharge it so that upon release of the reset button a transient charging pulse flows from conductor 12 through the capacitor 107, resistor 106, and into transistors Q7 and Q8 to render them conductive. With Q8 rendered conductive by this capacitor charging pulse the relay 1K is energized and contact 1K1 closes whereafter the train of pulses from Q6 maintains the relay energized.

When an event occurs in the monitor line such that a high current flows in the monitor line, the potential at junction 17 becomes less positive (low voltage) so that the normally conductive transistor Q1 tends to turn off. With the conduction of transistor Q1 reduced, the voltage drop across resistor 42 is less positive so that transistor Q2 becomes conductive. When Q2 is conductive, the voltage at the emitter of unijunction Q5 is maintained below the firing point of the unijunction and oscillation ceases. With no more pulses reaching transistors Q7 and Q8, they cease conducting and the relay 1K becomes de-energized. When the relay 1K drops out, contacts 1K1 open, the contact 1K2 makes with stationary contact 91 so that the alarm lamp '93 is illuminated. In addition the contact 1K3 closes allowing SCR Q9 to conduct to energize the bell or buzzer connected to terminal 124.

If an event occurs in the monitor line to reduce the line current from a normal value, the potential at sensing junction 21 is increased in a positive direction so that the conduction of the normally conductive transistor Q3 is reduced and a transistor Q4 becomes conductive causing the unijunction Q5 to be saturated so that oscillation ceases. In the same manner as described above for a high current, the loss of pulses causes the relay 1K to drop out and indicate alarm. When the unijunction Q5 is thus saturated it must be cut off before it can again go into oscillation. This is accomplished by one section of the Reset switch comprising contacts 103, 104 and 105. When the Reset switch is operated, the capacitor 110 is connected to the junction 21 and lowers the voltage on both sensor points 17 and 21. This results in the high current sensor shutting oif the unijunction. As the capacitor 110 becomes charged, the unijunction starts oscillating and if the monitor line has been readjusted to a normal current the oscillation continues. As has been described previously, the other half of the Reset switch is used to energize the relay 1K and close the relay contacts 1K1 thereby connecting the oscillator output to the relay circuit.

The Secure-Access switch 26 is used to reverse the current flow in the remote line and also switches in the Access lamps in place of the Secure lamps when the switch position is changed from a Secure to an Access position.

The test switch, a double-pole three-position switch, has a set position, as shown, in which the switch connects the unit with the external remote monitor line without adding resistance in series or in parallel with the line; a high position in which resistance is placed in parallel with the line and the unit will go into alarm since the current monitored by the apparatus will increase above the normal line current; and a low position in which resistance is placed in series with the line so that the unit will go into alarm since the current monitored by the apparatus decreases below the normal line current.

The bell control and Silence switch comprising SCR Q9 and the associated components function substantially as follows. When the monitor relay 1K is de-energized indicating an alarm condition, the contacts 1K3 close and the 24 volt DC supply is applied through the SCR to the bell circuit. To silence the bell, the SCR must be gated off by the Silence push-button switch. Silencing is accomplished when the switch is depressed so that the movable contact 125 makes electrical contact with 126 to apply a positive voltage transient through the capacitor 133 to the cathode of SCR Q9 to extinguish the SCR.

In one successful embodiment of the invention, the following component values were utilized.

6 Resistors:

15, 68 2.7K 16 c 1.5K 20 ohms 499 22 do 700 23 do 300 32 2.0K 40, 50 47K 42, 52 27K 44 hohms 500 54, 60, 116 1K '62, 65 1.07K 66, 10K 78 22K 81, 121 ohms 470 83 680K 86 c 390K 94 ohms 10 106 K 108, 131 ohms 100 112 do 56 115 370K Capacitors:

70 mfd 15 72, 117 mfd.. .1 76, 84 mfd.. .47 77 mfd .01 82, 90 mfd 35 107 mfd 2 110, 133 mfd.. 10 mfd 5 Q1, Q4, Q6, Q7 2N2923 Q2, Q3 2N3638 Q8 2N3053 The embodiments of the invention in which an exclusive property or right is claimed are defined as follows:

1. An alarm apparatus for sensing and indicating deviations in supervisory current above or below a predetermined normal level of current comprising:

a supervisory station having a pair of output terminals adapted to be connected to a two wire transmission line leading to a terminating impedance at a remote station;

a stable source of potential at said supervisory station;

a monitor line including impedance means connecting said source of potential to said output terminals to provide a normal level of current through said monitor line;

said monitor line further including means responsive to current magnitude in said line to produce potentials which are a function of said current magnitude;

normally oscillating unijunction transistor oscillator means having an output circuit and having an oscillation disabling input terminal, said means normally providing a train of pulses at said output circuit;

potential actuated disabling means connected between said current responsive means and said oscillator means input terminal; said disabling means being operative in response to a change in potential representing a deviation in current from said predetermined normal level to provide .a disabling signal to said oscillator means;

pulse activated means including signalling means operative to an alarm condition in response to a cessation of said oscillator pulses;

and pulse transmitting means connecting said oscillator means output circuit to said pulse activated means.

2. The apparatus according to claim 1 in which said stable source of potential is a regulated direct current source.

3. The apparatus according to claim 1 in which said monitor line impedance means and current responsive means comprises a plurality of resistive elements connected to form a voltage divider network.

4. The apparatus according to claim 1 in which said potential actuated disabling means comprises transistor means operative to a conductive state to disable said oscillator means.

5. The apparatus according to claim 1 in which said pulse activated means comprises transistor means having an input circuit and an output circuit, the output circuit having a relay in circuit therewith, the input circuit being connected by said pulse transmitting means to said oscillator means output circuit, said transistor means being rendered conductive by pulses received to maintain energized said relay so long as said pulses continue.

6. The apparatus according to claim 1 in which the References Cited UNITED STATES PATENTS 2/1962 Regis. 1/1969 Hansen 340-409 THOMAS B. HABECKER, Primary Examiner US. Cl. X.R. 340-253 

